From fbfda7b9f366f27b6905004f0367478559db553b Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Fri, 28 Aug 2026 18:07:00 +0200
Subject: [PATCH] test(transaction): add multi/exec transaction tests

---
 test/excache/transaction_test.exs | 111 ++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100644 test/excache/transaction_test.exs

diff --git a/test/excache/transaction_test.exs b/test/excache/transaction_test.exs
new file mode 100644
index 0000000..9d2b746
--- /dev/null
+++ b/test/excache/transaction_test.exs
@@ -0,0 +1,111 @@
+defmodule Excache.TransactionTest do
+  use Excache.Test.ServerCase, async: false
+
+  test "MULTI queues commands and EXEC applies them in order", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "a", "1"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["INCR", "a"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["GET", "a"])
+
+    assert {[{:simple, "OK"}, 2, "2"], conn} = Client.command(conn, ["EXEC"])
+    assert {"2", _conn} = Client.command(conn, ["GET", "a"])
+  end
+
+  test "DISCARD drops queued commands without applying them", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "gone", "v"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["DISCARD"])
+    assert {nil, _conn} = Client.command(conn, ["GET", "gone"])
+  end
+
+  test "EXEC without a prior MULTI is an error", %{conn: conn} do
+    assert {{:error, "ERR EXEC without MULTI"}, _conn} = Client.command(conn, ["EXEC"])
+  end
+
+  test "DISCARD without a prior MULTI is an error", %{conn: conn} do
+    assert {{:error, "ERR DISCARD without MULTI"}, _conn} = Client.command(conn, ["DISCARD"])
+  end
+
+  test "nested MULTI is rejected", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:error, "ERR MULTI calls can not be nested"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "OK"}, _conn} = Client.command(conn, ["DISCARD"])
+  end
+
+  test "an unknown command queued inside MULTI aborts the whole transaction", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "kept", "no"])
+
+    assert {{:error, "ERR unknown command 'NOTACOMMAND'"}, conn} =
+             Client.command(conn, ["NOTACOMMAND"])
+
+    assert {{:error, "ERR EXECABORT" <> _}, conn} = Client.command(conn, ["EXEC"])
+    assert {nil, _conn} = Client.command(conn, ["GET", "kept"])
+  end
+
+  test "WATCH aborts EXEC when the watched key changes before it runs", %{
+    port: port,
+    conn: conn
+  } do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["SET", "balance", "100"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["WATCH", "balance"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "balance", "0"])
+
+    interloper = Client.connect(port)
+    assert {{:simple, "OK"}, _interloper} = Client.command(interloper, ["SET", "balance", "50"])
+    Client.close(interloper)
+
+    assert {nil, conn} = Client.command(conn, ["EXEC"])
+    assert {"50", _conn} = Client.command(conn, ["GET", "balance"])
+  end
+
+  test "WATCH lets EXEC through when the watched key is untouched", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["SET", "balance", "100"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["WATCH", "balance"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "balance", "0"])
+    assert {[{:simple, "OK"}], conn} = Client.command(conn, ["EXEC"])
+    assert {"0", _conn} = Client.command(conn, ["GET", "balance"])
+  end
+
+  test "UNWATCH clears watches so a later EXEC is unaffected", %{port: port, conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["SET", "balance", "100"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["WATCH", "balance"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["UNWATCH"])
+
+    interloper = Client.connect(port)
+    assert {{:simple, "OK"}, _interloper} = Client.command(interloper, ["SET", "balance", "50"])
+    Client.close(interloper)
+
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "balance", "0"])
+    assert {[{:simple, "OK"}], conn} = Client.command(conn, ["EXEC"])
+    assert {"0", _conn} = Client.command(conn, ["GET", "balance"])
+  end
+
+  test "WATCH is rejected inside a MULTI block", %{conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+
+    assert {{:error, "ERR WATCH inside MULTI is not allowed"}, conn} =
+             Client.command(conn, ["WATCH", "key"])
+
+    assert {[], _conn} = Client.command(conn, ["EXEC"])
+  end
+
+  test "EXEC clears watches even after a successful run", %{port: port, conn: conn} do
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["SET", "balance", "100"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["WATCH", "balance"])
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "balance", "0"])
+    assert {[{:simple, "OK"}], conn} = Client.command(conn, ["EXEC"])
+
+    interloper = Client.connect(port)
+    assert {{:simple, "OK"}, _interloper} = Client.command(interloper, ["SET", "balance", "77"])
+    Client.close(interloper)
+
+    assert {{:simple, "OK"}, conn} = Client.command(conn, ["MULTI"])
+    assert {{:simple, "QUEUED"}, conn} = Client.command(conn, ["SET", "unrelated", "x"])
+    assert {[{:simple, "OK"}], _conn} = Client.command(conn, ["EXEC"])
+  end
+end